INTRODUCTION: Decentralized COVID-19 testing with antigen rapid diagnostic tests (Ag-RDT) is recommended by the Nigerian Centre for Disease Control for community-level services. These services have been provided in Primary Healthcare Centers, Community Pharmacies, and licensed "Patent Medicine Stores" that serve the least affluent communities. To support quality assurance, we applied an adapted version of SPI-RT (Stepwise Process for Improving the Quality of HIV Rapid and Recency Testing) to sites providing COVID-19-RDTs in Federal Capital Territory of Nigeria. METHODS: Between September 2022 and February 2023 community healthcare facilities (48 Community Pharmacies, 21 Patent Medicine Stores, 79 Primary Health Centers) were evaluated using Stepwise Process for Improving the Quality of SARS-CoV-2 Antigen Rapid Diagnostic Testing (SPI-RT) Checklist, tailored to the local implementation context. Evaluated domains included service quality, documents and records, personnel training and certification, safety, physical infrastructure, pre-testing phase, testing phase, and post-testing phase. Each facility received an overall score, expressed as a percentage indicating their performance level. RESULTS: 41/79 (52%) of Primary Health Centers scored at least 90% for service quality, as did 19/48 (40%) of pharmacies, with only 1/21 (4.8%) Patent Medicine Store. Apart from personnel training and certification, Primary Health Centers scored highest across most domains of service quality, followed by Community Pharmacies. The lowest median score in any domain was in the Patent Medicine Stores on testing and safety at 60% for both post-testing phase and safety. CONCLUSION: Primary Healthcare Centers and Community Pharmacies can provide quality decentralized testing for COVID-19. Patent Medicine Stores may need additional support including monitoring and quality improvement initiatives to ensure the provision of high-quality decentralized COVID-19 rapid testing services.